Persistent infection with a sexually transmitted infection known as human papillomavirus (HPV) is the primary cause of cervical cancer. Although Pap testing has significantly reduced the incidence of cervical cancer in the U.S., nearly 4,000 women died of cervical cancer in 2007. A prophylactic quadrivalent HPV vaccine (Gardasil) was recently approved for girls and women ages 9-26. The vaccine protects against infection by four HPV types responsible for over 90% of all genital warts and 70% of all cervical cancers. Routine HPV vaccination is recommended in girls ages 11-12 and "catch-up" vaccination among girls/women ages 13-26 who have not been vaccinated previously. Studies conducted before Gardasil's release found that young women expressed keen interest in the vaccine. Whether high acceptability will translate into high rates of vaccination, however, is unclear. In addition, little is known about effective methods for promoting HPV vaccination in young adults. The proposed research therefore will evaluate a behavioral intervention aimed at promoting catch-up vaccination among female college students, a population that is at high risk for HPV infection. The proposed intervention will apply the use of message framing, a theoretically grounded health communication strategy that involves motivating health behavior change through presentation of equivalent appeals framed in terms of either gains or losses. Message framing has proven to be a highly effective strategy for promoting behavior change across a wide range of health practices, including cancer screening and prevention behaviors. The first aim of the proposed randomized controlled experiment is to assess the effectiveness of a loss-framed intervention (relative to a gain-framed intervention and standard-of-care control) in promoting catch-up HPV vaccination. At baseline, participants will be randomly assigned to one of three interventions (loss, gain, control). Follow-up assessments will be conducted by telephone 2 and 8 months later to assess HPV vaccination status. Based on theory and previous research, exposure to a loss-framed intervention is hypothesized to increase HPV vaccination rates relative to the other two conditions. The second aim is to identify mediators of the intervention effect. Although several studies have attempted to uncover the cognitive and affective mechanisms underlying the effects of framed health messages on behavior, relatively few have been successful. In the proposed research, observed framing effects are expected to be mediated by increases in both perceived vulnerability to HPV infection and self-efficacy to receive the HPV vaccine. HPV infection represents a tremendous threat to public health. It is responsible for increasing medical costs, as well as the psychological and disease burden associated with abnormal Pap testing, genital warts, and cervical cancer. The long-term objectives of the proposed research are to facilitate the development of theory-based health communication interventions for promoting HPV vaccination and, ultimately, to reduce the incidence of cervical cancer.